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Harry R. Glahn

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Harry R. Glahn

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Harry R. Glahn

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The assumptions inherent in the determination of cloud top heights and areal coverage of clouds from infrared measurements made by satellites are discussed. The problems of interpretation caused by radiometer spatial resolution being of the same order of size as individual cloud elements are studied through mathematical simulation of the viewing process. An analysis of the simulated measurements from simple, specified cloud conditions produces quantitative estimates of the errors of interpretation.

It is found that individual cloud elements of a diameter slightly less than the viewed spot can be very misleading and the height of cloud tops might be judged to be several thousand feet below their true height; tops of larger clouds can be determined more accurately. If the actual height of the tops can be determined, either by the infrared measurements from large cloud masses or by other means, the areal coverage can be estimated rather well.

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Harry R. Glahn

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Canonical correlation analysis is concerned with the determination of a linear combination of each of two sets of variables such that the correlation between the two functions is a maximum. Under certain conditions this analysis is equivalent to discriminant analysis and under other conditions it is equivalent to multiple regression. In this paper the relationships among these techniques are discussed, equations relating to prediction by canonical variates are derived, a generalized correlation coefficient is proposed, and an example of canonical correlation analysis is presented.

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Harry R. Glahn

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Harry R. Glahn

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There is a popular misconception that the secant form of the Lambert conformal map projection is “better” than the tangent form. It is shown here that the two forms are equivalent; they are different only in the sense that the scale of the map quoted is usually true at the two secant latitudes for the secant projections and at the single tangent latitude for the tangent projection.

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Harry R. Glahn

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Harry R. Glahn

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Harry R. Glahn

A computer program is available that produces public weather forecasts in worded form from digital forecasts of weather elements. This program was designed to be implemented concurrently with the AFOS (Automation of Field Operations and Services) system. One version of the program operates on NOAA's large computer system and will send forecasts over the National Distribution Circuit; another version can be run on the local AFOS minicomputers.

This paper describes input to the program, the options available for its use, the decision processes whereby the forecast is constructed, the output of the program, and plans for its use. In addition, examples are shown of worded forecasts covering a variety of weather situations.

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HARRY R. GLAHN

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The regression screening and principal component techniques for developing forecast aids are investigated for their applicability to the objective forecasting of rainfall probabilities. The forecasting of summer rainfall in the Mississippi Delta is the particular problem studied. Subjective forecasts made for the area as well as objective forecasts are verified in terms of reductions of variance and saving over climatology. It is found that many of the forecast equations developed by regression screening and principal component techniques are not stable on test data. The results indicate that subjective screening of predictors is desirable before the regression screening is accomplished. It is found that useful aids can be developed with these linear techniques; at the same time the desirability of an approach that better integrates the physical processes of the atmosphere is indicated.

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